a PWC that does not meet the 2006 emission standards set by EPA

This is from the National Park Service website for Lake Powell/Glen Canyon. nps.gov

Regarding the Personal Watercraft 2-stroke, 4-stroke engine issue:

This rule only applies to PWCs. Regular boats do not apply.According to the Code of Federal Regulations Title 36, 7.70(e)(3): After December 31, 2012, no one may operate a PWC that does not meet the 2006 emission standards set by EPA for the manufacturing of two-stroke engines. A person operating a PWC that meets the EPA 2006 emission standards through the use of direct injection two-stroke or four-stroke engines, or the equivalent thereof, is not subject to this prohibition and will be allowed to operate as described in this section.

I looked for this a few years back, here it is. Maybe I'm late to the party